The present invention relates to refrigeration systems utilizing eutectic cold plates and more specifically to multi-temperature refrigeration systems utilizing eutectic cold plates in a refrigerated transport system.
Current refrigeration units for use on transport vehicles in which multiple temperatures are required are typically designed in one of two ways. First, two separate refrigeration systems can be used. This requires two compressors, two control systems, two reservoirs and two refrigerant charges. Second, a single refrigeration system can be used with the multi-temperature zones connected in series thereby allowing both zones to be cooled simultaneously.
Many problems exist with these two designs. If two separate refrigeration systems are employed, twice the refrigerant will be necessary. Refrigerant can be expensive, and it is therefore desirable to reduce to a minimum the total refrigerant needed. Further, the use of two systems increases the overall cost of the system by requiring duplications of equipment such as compressors, reservoirs, and condensers. Additionally, the additional maintenance and potential for refrigerant leakage is increased with multiple systems.
If the series design is utilized, the system will likely require a larger compressor due to the extended piping and associated pressure drops. Additionally, if only one zone requires cooling, both are cooled thereby unnecessarily increasing the work load on the system. It is therefore desirable to cool two or more areas using a single refrigeration system having multiple evaporators while avoiding the problem of unnecessarily cooling one area when only the other area requires cooling.
This invention provides a multi-temperature refrigeration system having a single refrigeration unit consisting of a compressor, a condenser, a reservoir, a plurality of valves, and piping, selectively coupled to one of at least two evaporators and expansion devices.
The valves are configured so that refrigerant can be provided to either of the evaporators in order to cool each evaporator independent of either of the evaporator(s). After sufficient cooling (e.g. after an associated cold plate is frozen), the refrigerant is pumped out of (i.e. drawn down from) that evaporator in preparation for providing refrigerant to other evaporators when needed. More specifically, when an evaporator requires cooling, the valves are configured such that the refrigeration system is coupled to that evaporator allowing refrigerant flow from the reservoir into the evaporator. Once sufficient cooling has occurred, the valves are reconfigured to allow the compressor to draw down refrigerant from the evaporator. The compressor continues to run until a predetermined pressure within the evaporator is reached. At this point the compressor is de-energized and the valves are configured such that flow is prevented. A microprocessor control is programmed to operate the valves and the compressor to maintain the desired state of cooling within the multi-temperature zones.